Apparatus for well logging



May 4, 1948. w. G. GREEN APPARATUS FOR WELL LOGGING Filed Dec. 1, 19545 2 Sheets-'Sheet 1 HIGH FREQUENCY 3 w E., M. I\| ...f R `S R O SRA E M M E W 7 U wm m w o oF vM u .E S S A v U R O L. E o www 5 5g s R o r y IO T E L R R R u, W R E E ./m AF. FDF b PT UN uw H HE P A C E. F M E m H A lu. o

MAGNETIZA'BLE ELEMENT I NVENTOR @M G. GREEN M fm1 ,y

ATTORNEYS May 4,1948. w. G. GREEN APPARATUS FOR WELL LOGGING Filed Deo. l, 1945 2 Sheets-Sheet 2 F/G. Z

AMPLIFIER INVENTOR A GREEN.

WILLIAM G BVZM L ATTORNEYS observation. The output voltage of the oscillator I9 is keyed to produce the desired depth indicating current pulses in accordance with movement of the magnetizable element I I into the bore hole I0. To this end, the element II is passed partially around the surface of a driving drum i4 which is shaft connected to a shutter disk I5 provided with a light slit I5a having the function of intermittently exposing the light sensitive surface of a photo electric cell i1 to the light radiated from alight source in the form of a lamp I8. The cell Il, in turn, controls the input circuit of a combined ampliiler and keying circuit I8. This circuit, which may be of conventional arrangement, performs the function of so controlling the oscillator I 8 that the latter unit can only operate to develop a high frequency output voltage when light is directed from the source I6 through the slit I5a to the sensitive surface of the cell I1.

For the purpose of developing a signal representative of the particular characteristic of the bore hole IU under observation and oi' recording this signal upon the magnetizable element II. signal generating and recording facilities are provided. the components of which are housed within a capsule 22 preferably formed of a plastic material or non-magnetic metal. This capsule or bomb is adapted to be dropped into the bore hole.

I0 and is provided along its longitudinal axis with internal walls defining a bore'2'i through which the magnetizable element ii is adapted to be threaded. A recording head 8i having pole face ends extending through the internal walls defining the bore 2l is utilised magnetically to record the signal representative of the characteristic under observation upon the element II as the capsule 22 is moved longitudinally of the bore hole. In order to obtain an indication of the pressure within the bore hole lil, a pressure responsive piston 29 exposed to the hole pressure is provided. Bpecilcally, this piston is movable within a cylinder 28 formed by re-entrant wall portions of the capsule 22, a coil spring 30 embracing the piston rod 29a being utilized to counterbalance the variable pressure exerted against the exposed surface of the piston 29.

All components of the signal generator are housed within the capsule 22. Specifically, the signal generating equipment comprises a pulse amplifier 6 having its output circuit coupled to the exciting winding Bic of the recording head ti and having an input circuit to which are delivered voltage pulses of varying amplitude accurately representative of the pressure indicated by the position of the pressure responsive piston 29. The pulses are generated through the action of a rotatable pulsing element 51 which is bridged across the input terminals of the amplifier 44 in series with the contacts of an on-oif switch and a variable portion of a potentiometer resistor 45, the terminals of which are connected to the terminals of a direct current source in the form of a battery 45. The switch 35 is provided with an actuating element which extends through the top wall of the capsule 22 for manual manipulation externally of the capsule. The magnitude of the voltage pulses periodically impressed across the input terminals of the amplier M through the pulsing element 4l is determined by the position of the adjustable wiper 48a along the potentiometer resistor 46. This wiper is directly connected mechanically to the piston rod 29a so that its position along the resistor 48, and hence the amplitude of the pulses developed by the pulsing element 4l. is directly related to the setting of `through the bore 21 of the capsule 22.

the piston 29 within the cylinder 28 and hence the pressure acting upon this piston. Preferably. the pulsing element 61 is driven at a constant predetermined speed by means of a suitable spring actuated clock mechanism, not shown, although if desired it may be driven by a small constant speed motor connected for energization from the current source ,45.

For the purpose of forming a permanent record of the `variable characteristic under observation and of accurately correlating the recorded characteristic with the depth of the bore hole, :facilities are provided for re-recording the signals and depth indications initially recorded on the magnetizable element II as this element is Withdrawn from the bore hole. These facilities comprise a multi-stylus strip .recorder 54 having stylus actuating coils 64a and 54h to which the signal representative of the characteristic under observation and the depth signals are respectively transmitted from the exciting winding of the head 2i when acting as a reproducing or pick up head. A low pass filter 5I followed by a signal amplifier 53 is included in the signal channel leading to the coil 54a to prevent the depth signals from exciting this coil. Similarly, a high pass filter 50 is employed to prevent the low frequency signal components representative of pressure variations within the bore hole from being impressed upon the coil 54h. In other words, this filter only passes the high frequency pulses representative of the well depth indications. These pulses are transmitted from the output terminals of the filter 50 through a combination amplifier and rectifier unit E2 to appear as direct current pulses in the coil lb.

Briefly to consider the manner in which the above described apparatus is employed to instrument the present improved method of well logging, it is pointed out that the first step required in using the apparatus is that of passing the free end of the magnetizable element II around the drum I4 and threading the same The sinker or weight I3 may now be attached to the end of the element II and positioned just at the surface entrance to the bore hole IIJ. During reeling out of the element I I, the capsule 22 is preferably so supported that this clement is free for unrestricted movement through the bore 2l of the capsule. With the sinker I3 flush with the earths surface at the mouth of the bore hole I 0, the key 20 may be actuated to its illustrated position wherein the contacts 20a and 20c are closed, and the two units I8 and iii Iconditioned for operation in the usual manner. Further, the lamp I6 should be energized in order to prepare the equipment for recording of the depth signals along the element II as it is lowered into the bore hole I0.

During movement of the magnetizable element longitudinally downward through the bore hole, this element obviously functions to rotate the drum I4 and the shutter disk I5. Each time the disk i5 is rotated through one revolution. light from the source I6 is transmitted through the slit I5a to impinge upon the light sensitive surface of the cell I1 and thus activate the high frequency oscillator I9 under the control of the amplier and keying circuit I8. In operating, this oscillator transmits a high frequency current pulse through the contacts 20a and 20c to the winding 2Ia of the recording head. This current pulse is recorded in the usual manner upon the element II at a predetermined point l tion.

astuces nements sans it om te understood that as the element i i is lowered into the bore hole, high frequency signal pulses are recorded at evenly spaced points along this element, It is also noted that the path of rotation of the light slit lila is of such length as to represent a prede teriniried length ci the element Il, such, for en ampie, as one foot, entering the bore hole it. It is pointed out further that the output freeuency of the oscillator it is so chosen as to permit the depth signals to loe readily illtereol from the low .frequency signals representative oi the here' hole characteristic under observa Another important feature of the present method of recording the depth signals upon the element il pertains to the fact that ro compensa-tion for stretch oi this element during rerecording of these signals is required. Specifically, as the element il is lowered into the hole, the portion thereoi moving past the recording head 2i is increasingly stretched. Since, however, the dish it is rotated through agiven angular increment in response to movement oi a given increment of the element il past the recording head tl regardless of the amount of tension and hence stretch in the element, the spacing between the depth signals as they are recorded upon the element li remains uniform.

dfitter the einher lil has been lowered to the bottom of the here hole it or to a desired position longitudinally of the bore hole, movement of the element is arrested. The next step is that ol lowering the capsule El into thebore hole for the purpose o generating and recording a signal representative of the particular physical characteristic under observation, i. e.. the pressure. This is accomplished oy first actuating the switch 3&5 to its closed circuit setting where in the contacts t3 are closed and than dropping the capsule into the here hole. With these switch contacts closed and the pulsing element 4l in operation, voltage pulses are impressed across the exciting winding lila oi the recording head di at the output side of the pulse amplifier il@ which have a variable amplitude directly related to the position ci the Wiper dta along the potentiometer resistor Accordingly. as the position of the piston il@ within the cylinder 2d changes in responseto variations in the iluid or gas pressure within the hole, to eiect corresponding changes in setting of the wiper @to along the resistor it, voltage pulses oi varying amplitude directly related. to the pressure under observation are impressed across the Winding 3io. These pulses are magnetically recorded in the usual manner upon the element il so that the amplitude o each pulse is accurately indicative of the pressure of the particular locationv of the capsule along the hole at which it is generated. Aliter the capsule lli? has reached the bottom of the hole to produce a continuous record of the pressure within. the bore hole, it engages the sinker i3 to he pulled out of the hole with the element il.

After the initial recording operation is thus completed, and as the capsule is pulled out oi the bore hole, the depth and pressure signals -recorded along the element il may be transcribed or re-recorded in permanent form. To this end, the key 2t is actuated to open the contacts Zta'. and 2do and close the contacts 2th and ltd. With the hey le in this position, the depth signal generating facilities are olovioushr rendered inoperative to excite the winding Zia. The next step is that of reeling in the magnetizable ele lli lit

dll

dit

ment il by suitably actuating the reel or spool il. is this element is pulled out of the bore hole iii, it moves past the recording head 2L, with the result that the signals recorded thereon are picked up by the winding il lo and transmitted to the input terminals of the high and low pass tilts-rs dll and ti. The filter llt is designed to pass only the high frequency depth signals and to reject the low frequency pressure signals. The depth signals as passed by this filter are amplified and rectified in the unit lit to appear as current pulses in the stylus actuating coil ttl. The resulting periodic redaction of the stylus contrailed hy this coil serves to produce a record' line Elib on the record strip to having odset points the therealong spaced distance accurately representing a given increment of hole depth. The low pass lter di functions to reject the high frequency depth 'signals and to pass only the low frequency signals representative oi pressure. These signals are amplified through the amplifier t@ and impressed upon the stylus actuating coil lita to effect periodic peaking oi the trace 5ta representing pressure. The amplitude of the peaks tdci thus produced in the trace litio is, oi course, a measure of the pressure at various points in the bore hole. Moreover, since the position oi the various pealrs longitudinally of the record strip t5 is accurately correlated with the depth indications ttc provided along the trace oth, the pressure at any particular point along the hole may be readily determined. Thus, a permanent record is produced which provides accurate data concerning the pressure within the hole at any point therealcns.

From the preceding explanation, it will be readily apparent that the factor ci stretch in the magnetizehle element il does not introduce any error whatever in correlating the pressure signals to the depth signals during the re-recording or transcribing operation. It is true that this element is, hy virtue ol its own cumulative weight, appreclably stretched along its upper region as it is lowered into the here hole, particu lerly at the depths ordinarily encountered in deep-hole logging operations. Error in correlation is avoided, however, since the Stretch is the same during both the initial recording and transcribing operations, as regards both the depth and pressure signals. Specirlcally, and hy way of example, during final movement ot the element ii into the well and initial movement out of the well during the renrecording operation, the er:- tent of elongation of that portion oi the element adjacent the top of the well due to stretch is exactly the same. This means that the signals are recorded on the element and picked up by the head 2i during the transcribing operation with exactly the same stretch elongation of the element at all points therealong. Hence the depth signals are related to the pressure signals with precision accuracy at all. points longitudinally of the permanent record strip 5t and iurther, the depth indicated by the accumulation of depth signals is accurately representative of the total here hole depth.

After the re-recording operation has heen completed, the sinker it may he removed from the end of the element il' and reeling in oi the element completed. The spool or, reel l2 upon which the element il is wound may, if desired, loe-preserved as an original record of the logging opa eration. Alternately, the record inscribed thereon may he magnetically erased as the element passes. from the drum it to the reel i2 during 7 the reeling in operation through the use of conventional erasing facilities. In the latter case the element li may obviously be used repeatedly for other logging operations.

Although the method and apparatus have been described in their use to provide a log of the pressure existent within a producing well, it will be understood that they are equally applicable to any well logging operation requiring instrument traverse of the bore hole. For example, they may be utilized to log the geological formation or structure traversed by a bore hole. This type of log may be obtained by modifying the signal generating equipment within the capsule 22 to include the facilities illustrated in Fig. 3 of the drawings. In the signal generator circuit there shown, the pulsing cam 41 is used in con- Junction with the current source 45 to deliver voltage pulses to spaced electrodes 4l projecting through the outer wall of the capsule 22. A pair of pick-up electrodes 48 are similarly mounted along the same wall of the capsule 22 intermediate the electrodes 48. The respective pick-up electrodes, which are insulated from each other and from the electrodes 48, are respectively connected to the input terminals of the amplifier 44, which in turn is connected to deliver its output to the winding lia of the recording head 3|.

With the described modication of the signal generating equipment, it will be understood that during operation of this equipment, and when the capsule 22 is dropped into a bore hole, each voltage pulse resulting from operation of the pulsing element 41 produces an electric field between the electrodes 4B. The character and intensity of this iield is, of course, influenced by the dielectric properties of the bore hole structure immediately adjacent the outer wall of the capsule 22. Thus, the resistivityv of the different formations through which the bore hole extends varies widely as between known geological structures of diilerent types, with a resulting change in the character and intensity of the electric field developed between the electrodes 48. Such changes are manifested by a change in the potential gradient between the pick-up electrodes 4I with the result that a signal voltage is produced at the output side of the amplifier 44, the variable characteristics of which may be analyzed to ascertain the geological structures through which the bore hole extends. age. as impressed upon the exciting winding )la of the recording head 3i, may be recorded upon the magnetizable element il and then transcribed into permanent record form along with the -depth signals, all in the exact manner explained above.

While there has been described what are at present considered to be the preferred embodiments of the invention, it will be understood that various modifications may be made therein which are within the true spirit and scope of the invention as deiined in the appended claims.

I claim:

l. Apparatus for recording a physical characteristic of a bore hole, comprising an elongated recording element, means for lowering said element into said hole so that it extends longitudinally of said hole from the top of said hole to a predetermined depth within said borehole, means for developing a signal representative of said characteristic at a predetermined depth in said hole, and means for recording said signal upon said element at a point therealong repre- This signal voltmoving 8 sentatlve of the hole depth at which said signal is developed.

2. Apparatus for recording a physical characteristic of a bore hole, comprising an elongated recording element. means for lowering said element into said hole so that it extends longitudinally of said hole, a signal generator, means for said signal generator longitudinally of said hole and said element, means for controlling said signal generator to develop a variable signal representative of said characteristic as said signal generator is moved longitudinally of said hole, and means for recording said signal upon said element as said generator is moved longitudinally of said hole.

3. Apparatus for recording a physical characteristic of a bore hole, comprising an elongated recording element, means for lowering said element into said hole so that it extends longitudinally of said hole from the top to a predetermined depth within said borehole and for withdrawing said element from said hole, means for developing a signal representative of said characteristic at a predetermined depth in said hole, means for recording said signal upon said element at a point therealong representative of the hole depth at which said signal is developed, means for translating said signal as said element is withdrawn from said hole, and means for recording the translated signal.

4. Apparatus for recording a physical characteristic of a bore hole, comprising an elongated recording element, means for lowering said element into said hole so that it extends longitudinally of said hole and for withdrawing said element from said hole, a signal generator, means for moving said signal generator longitudinally of said hole while said element remains stationary, means for controlling said signal generator to develop a variable signal representative of said characteristic as said signal generator is moved longitudinally of said hole, means for recording said signal upon said element as said generator is moved longitudinally of said hole, means for translating said signal as said element is withdrawn from said hole, and means for recording the translated signal.

5. Apparatus for recording a physical characteristic of a bore hole, comprising an elongated recording element, means for lowering said element into said hole so that it extends longitudinally of said hole from the top to a predetermined depth within said borehole and for withdrawing said element from said hole, means for recording depth marking signals upon'said element as said element is lowered into said hole, means for developing a signal representative of said characteristic at a predetermined depth in said hole, means for recording said signal upon said element at a point thereaiong representative of the hole depth at which said signal is developed, means for translating said signals as said element is withdrawn from said hole, and means for recording the translated signals.

6. Apparatus for recording a variable physical characteristic of a bore hole, comprising an elongated recording element, means for lowering said element into said hole so that it extends longitudinally of said hole and for withdrawing said element from said hole, means for recording depth marking signals upon said element as said element is lowered into said hole, a signal generator, means for moving said signal generator longitudinally of said hole while said element remains stationary, means for controlling said I 10 signal generator to develop a variable signal m CES representative ot said characteristic as said signal R EN CITED generator is moved longitudinally of said ho1e. The following references are of record in the means for recording said signal upon said ele- 111e 0f- -thiS Patent: v ment as said generator is moved longitudinally 5 UNITED STATES PATENTS of said hole. means for translating said signals f as said element is withdrawn from said hole, and Number Name Dte l 2,230,502 Pearson Feb. 4, 1941 means for recording the trans ated signals 2,288,278 Howell u June 3o' 1942 Winn 2,338,991 Arnold Jan. 11, 1944 M G' GREEN' lo 2,371,628 Krasnow Mar. 20, 1945 

